Pitch cartridge for electrode joint



y 7, 1958 H. v. JOHNSON ET AL PITCH CARTRIDGE FOR ELECTRODE JOINT Original Filed OC'b. 12, 1954 Mei'al Fpil 2 5 Wrappmg INVENTORS HARRY v. JOHNSON NEAL JOHNSON BY %1#? ATTORNEY United PITCH CARTRIDGE FOR ELECTRODE JGINT Harry V. Johnson and Neal J. Johnson, Niagara Falls,

N. '11, assignors to Union arhide Corporation, a corporation of New York 1 Claim. (Cl. 2136-34) This invention relates to a pitch cartridge for a joint between sections of an electric furnace electrode and has for an object to provide a cartridge for an improved joint of this class which is easier to make and assemble and has less danger of the pitch melting prematurely.

After the invention of Patent No. 2,510,230, it was discovered that a joint less in danger of nipple rupture could be provided by the provision of a pitch reservoir opening onto the end face of an electrode section so that when the pitch melted, it iiowed into the pores and craviccs and bonded the contacting end faces, thus transmitting much of the flerural stresses between the electrode sections directly without having to have them pass largely through the nipple. The clearance spaces around the nipple threads were substantially free of any pitch thereby enabling the nipple to slide or tilt slightly with respect to the electrode sections under flexure. A later improvement sought the same freedom from flexure in the nipple with satisfactory electrical conductivity in the end face contact by eliminating the itch reservoir in the end face and transferring it to each end of the nipple with only about 10% to 25% of the thread clearance space volume being filled with pitch.

According to this invention, by the use of a pitch cartridge to be described, a satisfactory electrode joint has been developed which possesses the advantages of a nippic that does not have to transmit a major portion of liexural stresses between electrode sections, has satisfactory electrical conductivity, adequate tightness to prevent an electrode section coming unscrewed with respect to the nipple, foolproofness whereby it is immaterial which end of a section and nipple is at the top or bottom, requires less pitch or other thermal setting bonding material, is one in which it is simpler and easier to form the pitch reservoir and install the pitch therein, and this joint is constructed to reduce the danger of the pitch flowing out of the reservoir prematurely and before the joint has been fully formed.

Specifically the nipple is provided adjacent each end with a diametral or radial recess into which the pitch or other thermal setting binder is inserted. The pitch is preshaped into the form of a stick of a size to be easily inserted in the recesses adjacent each end of the nipple, and the pitch is surrounded by a thermal insulating wrapper which delays the time required for the pitch to melt to an amount such that when the pitch cartridge is inserted in a nipple heated to a temperature above the melting point of the pitch, there will be ample time for the joint to be fully assembled after the last stick of pitch has been inserted. Upon heating, the pitch melts and flows into only about 10% of the thread clearance volume and adjacent each end of the nipple.

Referring to the drawing:

Fig. 1 is a longitudinal section through an electrode joint embodying this invention;

Fig. 2 is a longitudinal section of a modified construction;

rates 5 atent Fig. 3 is an enlarged detail of the area shown within the circle designated 3 in Fig. 1; and

Fig. 4 is a perspective showing the pitch cartridge.

The furnace electrode joint in Fig. 1 comprises the lower electrode section 10, the. upper electrode section 11 and the nipple 12 in threaded engagement with each section holding their end faces in mechanical and electrical contact as shown at 13. A diametral recess 14 is bored into the upper portion of the nipple l2 and a similar recess 15 adjacent the lower end of the nipple is also cut. Within each reservoir or recess is a preformed cartridge 16 of pitch having a melting temperature between about C. and 200 C. As is well known in the art, the pitch in this cartridge melts. on heating. It flows out of its diametral recess into the clearance spaces indicated in Fig. 3, where on further heating, it carbonizes and bonds the nipple to the electrode section against the sections coming unscrewed in use. In the present instance the quantity of pitch, however, is insuflicient to fill all such clearance spaces and only about 10% to 20% of the volume of such clearance spaces is supplied with this pitch and the pitch is located adjacent the ends of the nipple after it has become set. In this way the joint is not so stiff but permits a slight tilting or sliding of the nipple with respect to each section in order that fiexural stresses may not in large measure have to be borne by the nipple because the joint is usually of less strength to Withstand such stresses than are the electrode sections.

The preformed cartridge of pitch has a wrapper of thermal insulatin material around it as shown in Figs. 3 and 4. Around the outside or" the cartridge is a layer of aluminum foil 17 to reflect radiant heat from the nipple from penetrating the cartridge and melting the pitch prematurely. Between the pitch 19 and the foil 17 is a layer of fibrous insulating material 18 to delay conduction of heat from the nipple to the pitch. In this case the fibrous material 13 is constituted by about 14 layers of kraft paper in a cartridge for a 20 inch diameter electrode. The efifect of this wrapping is to delay the melting of the pitch 19 as much as one to six minutes before it flows into the helical clearance spaces 29.

In Fig. 2, wherein is represented a furnace electrode joint comprising a lower electrode section 10a, an upper electrode section Ila, and a connecting nipple 12a in threaded engagement therewith, holding the sections in electric and mechanical contact as shown at 13a, the pitch recesses 14a and 15:: are radial and the pitch cartridge 16a is of shorter length than is the cartridge in Fig. 1 for the same size electrode and nipple. No large number of radial cartridges will be needed because the clearance space to be filled is small.

Instead of a conductive cementitious binding material like pitch, it has been found that a non-conductive cementitious binder may also be used in place of the pitch, but preferably such a binder should be thermal setting. Examples of non-conductive binders include water glass and Saureisen cement.

The cartridge recesses in the nipple are drilled adjacent the top and bottom without having to invert or change the position of the nipple.

In locations where the electrode sections must be connected close to the top of the furnace due to the absence of headroom or because a long electrode slip cannot be tolerated within the furnace, it has been found that the thermally insulated pitch cartridge of this invention is especially needed. In those installations where large headroom above the furnace is available, the electrode section may be connected far enough away from the furnace roof for the thermally insulated pitch cartridge to be unnecessary. Where the headroom is not large, a cartridge is placed into one end of the nipple before the v V c; ,2 nipple is threaded intothe heated lower section. The nipple is then screwed into that lower section for half its "length; Hours later a pitch cartridge is placed into the upper recess 14 of the nipple just before the upper electrode section is to be .secured in place, The threading of each electrode section onto it sinipple sho'ulditalre not over a minute and the delay occasioned by the thermal insulation around the pitch is adequate to prevent the to carboncontact, Another way 'in which the joint is made to have the nipple with onecartridge inserted into a'cold electrode section with the section arranged horiiontally,,then when a section is moved to a vertical position apitch cartridgeis' placed in the lower end of the nipple just before that nipple is threaded into the hot lower electrode section. I I j s 7.

"Among the advantages of this invention may be mention ed the fact that a suitable electrode'joiut has been provided which is simple and less costly than have been the prior art' joints. .A delay. of one to sm minutes at fords'protection against premature melting of the pitch beforethe parts of the joints are fully assembled. The

nipple and the electrode sections are both capable of being. attached with either end upward, thus providing a foolproof jointpthat is one in which the workman need not be required to be sure that one end of the nipple or of an electrode section is intended to be at the bottom of thejoint As compared with the joint of prior patent construction 2,510,230, the present joint is free of the disadvantage of having considerable nipple breakage due to the joint being too stifif. As compared with thejelectrode joint in the'prior application of H. V. Johnson,

Serial No. 300,243 ,'file d July 22, 1952, now abandoned, the joint of the present invention is morenearly foolproof since either end of'either the nipple or the electrode section may be placed uppermost or lowermost, but

'it makes no difference which. -As compared to that same priorconstruction, the joint of this invention is slightly pitch from melting prematurely and preventing carbon more conductive for an electrode of the same size due to the'fact that no portion of a meeting ofend faces of either electrode section 'in this invention is prevented from having any good contact with the other or contiguous meeting end face. In that prior mentioned application, Serial No. 300,243, a minor portion of the meeting end faces of one or both electrode sections was eliminated from afiording good contact by the fact reservoir was formed within that end face As compared with the joint in the prior application of. Johnson, et a1. Serial No. 379,566, filed September 11, 1953 for Furnace Electrode Joint, the construction of the present invention requires lesspitch because not so much pitch has to remain in the pitch reservoir as is the case in that last mentioned application if it is to be considered; capable of comparable foolproof ness. In that prior construction the pitch reservoirs were axially disposed and almost half" of the pitchin that reservoir was not usableQ The drilling of the holes for the pitch in said aforementioned application was more diflicult because the nipple had to be turned over after having one pitch reservoir-drilled, V

in orderfor the reservoir at the opposite end of the nipple to be formed.

With a nipple 10.75 by 14 inches, the pitch reservoirs 16 and 16a were placed about one and a half inches from each end. The quantity of pitch found desirable is in the range of .02 to .11 of a pound for this foregoing the melting point of said pitch are encountered, said pitch having "a melting temperature between about C. and 200 C., said cartridge being provided with a fibrous, thermally insulating jacket to defer the time of that a pitch application Serial melting said pitch for overa minute, despite the fact,

that said nipple is at. a temperature above the melting point of said pitch, said jacket being consumable at a temperature well above that at which said pitch melts and having an outer wrapping of heat-reflective foil.

7 References Cited in the file of this patent UNITED, STATES PATENTS 2,348,622 Heilman' May 9, 1944 V FOREIGN PATENTS 63,481 7 France Apr. 13, 1955 7 

